1. Field of the Invention
The present invention generally relates to image forming apparatuses and, more particularly, to an image forming apparatus, such as a printer, a copy machine, a facsimile apparatus or a digital compound machine, which is capable forming an image at a plurality of image formation levels.
2. Description of the Related Art
In image forming apparatuses, such as a printer, a copy machine, a facsimile apparatus or a digital compound machine, when an error occurs during an image forming operation, conventionally, the image forming operation is interrupted, and the image forming apparatus is set in a standby state until the cause of the error is eliminated. Therefore, if an error occurs, the image forming operation cannot be resumed until a user eliminates the cause of the error. For this reason, as a result, a completion of the image formation is delayed very much. In order to avoid such as problem, the user must supervise the state of the image forming apparatus, which causes a problem that working efficiency is bad.
Especially, when a plurality of users (or host apparatuses) share an image forming apparatus, there is a case in which a job requested by one of the users cannot be performed due to an error which has occurred during an execution of a job which the one of the user does not know, which problem is serious.
Japanese Laid-Open Patent Application No. 2001-341383 discloses a printer, which solves the above-mentioned problem. This printer cancels a job, if an error occurs during execution of the job and the error can be eliminated by canceling the job, and automatically releases the error state which is eliminated by the cancellation of the job. When the error state is released to an extent that an image formation is performed, an interrupted image forming operation is resumed. According to such a printer, even when an error occurs during execution of a certain job and the error does not cause a trouble in execution of future jobs, a next job can be performed automatically. Therefore, working efficiency can be improved.
Therefore, in the above-mentioned printer, when resuming an image forming operation automatically after occurrence of an error, the job which caused the occurrence of the error is forcibly canceled. In such a case, a user has to make an instruction for printing again so as to perform an image forming operation concerning the canceled job. However, when the error is relevant only to functions, which are not directly related to the image forming operation, the image forming operation may be performed without canceling the whole job. Therefore, canceling the job also in such a case may cause a problem of deterioration of working efficiency.